Means for controlling electrostatic charge on the rear window of a cathode-ray tube

ABSTRACT

Means for controlling the electrostatic charge on the rearwindow of a cathode-ray tube wherein a substantially annularshaped optical access rear-window is oriented in the tube envelope in substantially symmetrical relationship to the longitudinal axis thereof. The window which provides a substantially annular viewing area from observing the electron impinged side of the screen has electrical conductive means symmetrically and discretely associated therewith to control the electrostatic charge thereon.

United States Patent Bossers 1 Feb. 15, 1972 541 MEANs FOR CONTROLLING ELECTROSTATIC CHARGE ON THE REAR WINDOW OF A CATHODE-RAY TUBE [72] Inventor: Chris F. Bosser's, l6 Johnston Street, Seneca Falls, N.Y. 13148 {221 Filed: July 23, 1970 211 Appl.No.: 57,473

Related US. Application Data [62-] Division of Ser. No. 785,648, Dec. 20, 1968'.

521 U.S.Cl. ..313/92R,3l3/64 [51] Int. Cl ..H0lj 29/00, l-lOlj 29/89, HOlj 29/46 I [58] FieldofSearch ........3l3/92R [56] References Cited 7 UNITED STATES PATENTS 7 2,077,270 4/1937 Schlesinger .Q ..3l3/92 R X Knoll ..3l3/92 R X Szegho ..3 1 3/92 Primary Examiner-Robert Segal Attorney-Norman .l. OMalley, Donald R. Castle and Frederick H. Rinn 7 [s7] ABSTRACT Means for controlling the electrostatic charge on the rear-win dow of a cathode-ray tube wherein a substantially annularshaped optical access rear-window is oriented in the tube envelope in substantially symmetrical relationshiprto the longitudinal axis thereof. The window which provides a substantially annular viewing area from Observing the electron impinged side of the screen has electrical conductive means symmetrically and discretely associated therewith'to control the electrostatic charge thereon.-

1 Claim, Drawing Figures PATENTEDFEB 15 I972 SHEET 1 OF 2 INVENTOR. CHRIS F 505SR5 ATTORNEY PATENTEDFEB15 m2 SHEET 2 BF 2 INVENTOR. CHRIS E BOSSERS ATTORNEY MEANS FOR CONTROLLING ELECTROSTATIC CHARGE ON THE REAR TUBE CROSS REFERENCE TO RELATED APPLICATIONS This application is-"a'divisional application of Ser. No.

785,648, filed Dec.'20, 1968, which is assigned to the assignee cations are: Ser. No. 785,646 Cathode Ray Tube Having an Annular Shaped Rear Window," and Ser. No. 785,647 Method and Apparatus forFabricating a Cathode Ray Tube Having an Annular Shaped Rear Window."

BACKGROUND or THE INVENTION The invention relates to cathode-ray tubes and more particularly to an improved rear-window type of cathode-ray tube having means therein for controlling the electrostatic charge on. the rear window thereof. In certain types of information display systems, rear-window cathode-ray tubes are employed to facilitate full presentation and observation; of the display. Such tubes not only provide the conventional frontal viewing area but also have one or more portal provisions oriented in the funnel portion of the 'tube envelope topermitviewingof WINDOW or A CATHODE-RAY FIGS. 5, 6 and 7 are enlarged sectional view of substantially the annular plate and 'neck section seal region showing several I shield embodiments protruding into the bulb portion.

I therein. The light transmissive plate 19 forms an annular shaped optical window which provides extensive visual access aforedescribed drawings. p is shown a rear-window DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following specification and appended claimsin connection with the With reference to FIG. 1 there cathode-ray tube 11 having a face panel portion 13 upon which is interiorly disposed a cathodoluminescent screen 15. Integral with the face panel portion is the funnel orlhulb por-- 5 tion 17 to which is sealed a substantially transparent annular plate 19.0f optical quality. A tubular neck section 21 is sealed to the centrally oriented aperture 23 of the annular plate to I complete the envelope structure. At least one electron source 25 is mounted in the tubular neck in a manner to beam electrons to the screento form a cathodoluminescent image to the rear of the screen.

A round tube is'shown and described such as, for example, I I

. one having an external envelope diameter within the range of the rear surface of the screen. Through this type of funnel oriented viewing port, it is possible to observe, photograph, or project a superimposed image on the information displayedon the screen without interferring with the frontal observation tubes are restricted to one or two observation ports, there is an improvedtype of rear-window tube which incorporates an annular-shaped rear-windowin the envelope in substantially symmetrical relationship to the longitudinal axis of the tube. While this annular windowaffords extensive. and adelectron beam or beams passing through the centrally oriented aperture therein. I

OBJECTS AND SUMMARY OF. THE INVENTION .tionby the provision of means for controlling the electrostatic 5 to 6 .inches. It is not intended that the size or shape be limiting. In addition, the term annular" as used herein is intended I toinclude any shape of substantially continuous optical view- 5 ing' window oriented to surround the axial oriented tubular neck portion of the tube. thereof. While a large'number of conventional rear-window i In greater detail, the tube 'l'lhas a emetic jointures therebetween.

' vantageous utilization, there are sometimes occasions when an electrostatic charge builds up thereon to adversely affect the g 13 by conventional means as, for example by the settling charge on the annular shaped window of an improved rear- 1 windowcathode-ray tube having an envelopecomprising a bulb portion'perimetrically sealed to a rear-window annular plate and a tubular neck section joined to the substantially centrally oriented aperture in the annular window. The electrostatic charge which may be present on the annular .plate is controlled by a plurality of spaced-apart radially oriented electrically conductive strips which are applied to the interior surface of the window to provide connective means with the neck coating to dissipate the charge from the window area. Thus, there is provided a tube having an annular-shaped rearwindow that is substantially free .of electrostatic charge and which permits simultaneous back-of-the-screen projection, photographing and observation of the information displayed on the cathodoluminescent screen of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the rear-window cathode-ray tube of the invention;

FIGS. 2, 3 and 4 are plan views taken along the line 2-2 of FIG. 1 illustrating the expansive area of the annular rear-win dow portal and several embodiments of the electrical conductive means associated therewith; and

The substantially planar face panel portion 13 is of a nonbrowning-type glass hermetically sealed with the compatibly formed bulb portion 17. V

A cathodoluminescent screen 15 of {suitable phosphor material is disposed on the interior surface of the face panel technique.

A substantially transparent annular plate I9, such as 0-12 optical quality glass has outer and inner peripheries or boundaries'29 and 31 respectively, defining annular region 33 therebetween which constitutes an annular shaped planar viewing window that is spacedly related in a substantially sy m metrical manner about thelongitudinal axis of the tube. The inner periphery 31 defines a substantially centrally oriented opening or aperture 32, while the outer periphery 29 of the annular plate is formed to substantially perimetrically match J the compatible bulb portion to which it is hermetically sealed I by glass solder or frit 37 which has a melting temperature much lower than the softening temperatures of the respective glass portions joined together.

A substantially tubular neck section 21 is formed to be seated and sealed in the centrally oriented aperture 23 in the I annular plate by utilizing a continuous band therebeween of glass frit 37' similar to that used in making the aforementioned bulb-to-plate seal. Q j I One or more electron gun(s) is/are positioned within the neck section of the tubein a manner to beam electrons to the screen. As shown, an undetailed source of electrons 25 denotes the presence of one or several guns. In this instance, both focusing and deflection are accomplished by electrostatic means which eliminates the need for externally oriented yoke means.

A stem portion 45, which supports the source of electrons 25, is hermetically sealed to the terminal end of the neck section 21. Electrical connective means 47 extend from the stem through the base 49 to provide external connections for the tube.

longitudinal axis 12 ex tending therethrough from the face to the 'base' portionsthereof. The componental parts of the envelope structure The interior surface of the bulb portion 17 has two separated bands of conductive material, such as aquadag, applied thereto. The first of these bands 51 is oriented adjacent the screen area and makes electrical contact with the high voltage anode button 53 located in the bulb or funnel portion I7. The second conductive band 55, of similar material, is disposed on the bulb wall near the optical window 33. Electri cally joining the two bands is a conventional accelerating spiral 57 of resistive material.

A neck conductive band 59 is applied to the upper part the tubular neck section 21. Electrical connection between this band and the electron source 25 is effected by the usual type of connective means 61.

Operation of the tube is dependent upon an electrical connection between the neck conductive band 59 and the second conductive band 55 on the bulb. This is expeditiously effected by applying one or more conductive paths 63 to the inner bulb surface to extend from the second band thereon to the annular optical plate I9, whereupon at least one radial conductive stripe 65, such as aquadag or tin oxide, is applied to the surface 34 to complete an electrical path between the neck and bulb conductive coatings.

There is an electrostatic charge effect that may at times build up on the interior surface of the annular plate during operation of the tube. This electrostatic charge is the result of spurious electron impingement and secondary emission. The

I gortion of the envelope. These rings aped protrusions shield t e electron beams from the influence of the Charge. which'may be present in the plate. The maximum height "Z" of the respective shield means should be such as to not interfere with the angle of deflection Lu of the electron beam or the angle of presence of this charge on the annular window area deleteriously affects .the axially related stream of electrons beamed through the centrally oriented aperture in the plate.

In referring to the Figures. it has been found that several constructional embodiments can be utilized to minimize electrostatic charge buildup and prevent the undesirable effects thereof. With particular reference to FIG. 2 a plurality of width LB of the optics of the photographic device 7 I.

In FIG. 5, the shield member 73 is an extension of the neck portion 21'. The neck section is formed to have a bulging peripheral rib 75 of a diameter slightly larger than that of the centrally oriented aperture 23 to thereby provide a seat for the annular. plate 19. A continuous annular layer of frit 77 disposed betweenthe plate and the neck section provides a hermetic jointure. The conductive coating of the neck band 59 is continued to cover at least the inner surface of the shield member. I

FIG. 6 illustrates a separate ring-shaped glass or ceramic shield member 79 which is seated in and frit-sealed to the annular plate 19. The neck band conductive coating 59 is 5 likewise extended to at least cover the inner surface of this shield member.

FIG. 7 represents still another shield embodiment in the shape of a metallic ring 81 having a plurality. of lugs 83 extending to the seal region and there embedded in the frit 37'. The material, such as NiCr-Fe alloy, has a thermal expansion I coefficient that is compatible with the glass of the envelope.

spaced apart radially oriented conductive stripes 66 making common connections with the bulb and neck conductive bands may be used to uniformly dissipate and conduct away the electrostatic charge from the annular window area. This array of conductive sectors provides a plurality of annular viewing areas 68 therebetween. While four conductive stripes or sectors are shown, such number is not to be considered as limiting;

FIG. 3 illustrates another charge reducing embodiment in the form of an annular gridlike metallic conductive medium 67 comprised of afne wire construction which is oriented relative to the interior surface of the window. The term gridlike" is intended to include a radial array of wires, web. mesh or foraminous material. Such material may introduce a degree of opacity or reduced transmission to the window area. Since the plane of orientation of this material is spacedly remote from the screen. it is out of focus with the image in or on the screen 15 and presents a degree of optical interference which, in some instances, may not be objectional. If desired, cutout areas 70 can be made in the gridlike material to provide multiple window areas. Each gridlike structure has multiple tabs 64 or projections, several of which are shown extending peripherally therefrom to facilitate affixation to the respective seal areas; The material. from which the gridlike structures are fabricated, has a thermal expansion coefficient similar to that of the glass of the annular window, such, for example Ni-Cr-Fe alloy.

In FIG. 4. the annular window 33 is shown as having a substantially light transmissive conductive medium or coating 69, such as tin oxide, uniformly applied to the interior surface of the window. This material also exhibits a degree of opacity, but as with the gridlike construction, it also is out of focus with the screen image and presents a degree of uniform optical interference. This type of reduced optical transmission may be acceptable in certain instances where viewing provisions are desired.

FIGS. 5, 6 and 7 illustrate additional embodiments for contion, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

lclaim:

l. A rear-window cathode-ray tube having a longitudinal axis, a cathodoluminescent screen, at least one electron source positioned in said tube relative to saidscreen to beam electrons thereto, and a glass envelope comprising panel, bulb and neck portions formed to provide an enclosure for, said screen and said electron source, said envelope having a substantially annular shaped optical access window oriented between said bulb and neck portions in substantially symmetrical relationship about said longitudinal axis and in relation to said screen to provide a substantially annular viewing area for observing the electron impinged side of said screen, and means for controlling electrostatic charge effects on said annular-shaped window wherein said bulb and said neck portions have discrete areas of electrically conductive coating applied to the respective interior surfaces thereof, said annular shaped window located therebetween having substantially symmetrically oriented conductive means associated therewith to electrically connect said conductive coatings,

G U O O Q H050 UNITED STATES PATENT ()FFIQE (5/69) g i H a a CENPECATE C UH Patent No. 3, I Dated F b y 15,

lnventol-(s) Chris F. Bossers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Please add the following to the front page:

[73]-"Assignee: Sylvania Electric Products Inc.

In the Abstract, Line 6, "from" should read for Column 1', Line 59, "strips" should read stripes Column 3, Line 68, "where viewing" should read where extensive viewing Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M, FLETCHER,JR. Attesting Officer 

1. A rear-window cathode-ray tube having a longitudinal axis, a cathodoluminescent screen, at least one electron source positioned in said tube relative to said screen to beam electrons thereto, and a glass envelope comprising panel, bulb and neck portions formed to provide an enclosure for said screen and said electron source, said envelope having a substantially annular shaped optical access window oriented between said bulb and neck portions in substantially symmetrical relationship about said longitudinal axis and in relation to said screen to provide a substantially annular viewing area for observing the electron impinged side of said screen, and means for controlling electrostatic charge effects on said annular-shaped window wherein said bulb And said neck portions have discrete areas of electrically conductive coating applied to the respective interior surfaces thereof, said annular shaped window located therebetween having substantially symmetrically oriented conductive means associated therewith to electrically connect said conductive coatings, said means being in the form of a plurality of spaced apart radially oriented conductive strips applied to the interior surface of said window to provide connective means between the respective bulb and neck coatings and means for dissipating electrostatic charge from said window portion to prevent said charge effects from interfering with the performance of said tube. 